The present invention relates to a method of producing a modified polypropylene by graft polymerization at a high graft ratio without suffering from a decrease in molecular weight.
Since polypropylene is inexpensive and excellent in moldability, insulation, chemical resistance, mechanical strength, etc., it is widely used in various applications such as films, fibers, moldings, etc.
However, polypropylene is poor in chemical properties such as adhesion, coatability, printability, hydrophilic properties, etc. due to its structure. To solve these problems, an investigation has been being conducted on the graft polymerization of polypropylene with various unsaturated compound monomers.
The graft polymerization of polypropylene with unsaturated compound monomers is usually conducted by treating polypropylene with irradiation of electron beams, ultraviolet rays, etc. or with ozone to generate radicals and then reacting the treated polypropylene with unsaturated compound monomers, or by reacting polypropylene with unsaturated compound monomers in the presence of radical generators such as organic peroxides.
However, in such conventional methods, the scission of polypropylene chains takes place in the process of radical generation, resulting in a low molecular weight and a low graft ratio. Accordingly, the resulting modified polypropylenes suffer from unpleasant odors and coloring due to unreacted monomers, failing to have desired properties. Further, since the resulting modified polypropylenes have too small of a molecular weight, moldings containing them are poor in strength.